Purpose::
This study examined the capacity of a surface-modified poly(ethyleneglycol)/poly(acrylic acid) (PEG/PAA) hydrogel, designed to serveas a artificial cornea, to sustain biologically active collagentype I, which promotes surface corneal epithelialization.

Methods::
PEG/PAA hydrogel surfaces were modified with varying densitiesof collagen type I through a photoreactive, bifunctional azide-active-esterlinker. The bioactivity of the collagen tethered to the hydrogelswas quantified using a conformation-specific antibody in anenzyme-linked immunosorbent assay (ELISA). The absorbances werecompared to a standard curve of collagen adsorbed at varyingconcentrations to MaxiSorp polystyrene. Heat-denatured collagenwas adsorbed to MaxiSorp polystyrene as a negative control.

Results::
Reactivity to bioactive collagen type I increased as a functionof collagen reacted to the surface. A comparable trend was demonstratedby collagen adsorbed to the Maxisorp surfaces. Heat-denaturedcollagen did not produce a signal, indicating that the conformation-specificantibody could not detect inactive collagen.

Conclusions::
One of the challenges in designing a polymer that supports surfacecovalent immobilization of proteins is surface-induced denaturation.These results, however, indicate that proteins remain in theirnative conformation when tethered to the PEG/PAA hydrogel surface.Therefore, this material can be used to tether proteins, suchas collagen type I, to enhance epithelial cell growth and adhesion.